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This is an example about how to add eventfd support to the current KAIO code, in order to enable KAIO to post readiness events to a pollable fd (hence compatible with POSIX select/poll). The KAIO code simply signals the eventfd fd when events are ready, and this triggers a POLLIN in the fd. This patch uses a reserved for future use member of the struct iocb to pass an eventfd file descriptor, that KAIO will use to post events every time a request completes. At that point, an aio_getevents() will return the completed result to a struct io_event. I made a quick test program to verify the patch, and it runs fine here: http://www.xmailserver.org/eventfd-aio-test.c The test program uses poll(2), but it'd, of course, work with select and epoll too. This can allow to schedule both block I/O and other poll-able devices requests, and wait for results using select/poll/epoll. In a typical scenario, an application would submit KAIO request using aio_submit(), and will also use epoll_ctl() on the whole other class of devices (that with the addition of signals, timers and user events, now it's pretty much complete), and then would: epoll_wait(...); for_each_event { if (curr_event_is_kaiofd) { aio_getevents(); dispatch_aio_events(); } else { dispatch_epoll_event(); } } Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
111 lines
3.0 KiB
C
111 lines
3.0 KiB
C
/* include/linux/aio_abi.h
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*
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* Copyright 2000,2001,2002 Red Hat.
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*
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* Written by Benjamin LaHaise <bcrl@kvack.org>
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*
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* Distribute under the terms of the GPLv2 (see ../../COPYING) or under
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* the following terms.
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*
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* Permission to use, copy, modify, and distribute this software and its
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* documentation is hereby granted, provided that the above copyright
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* notice appears in all copies. This software is provided without any
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* warranty, express or implied. Red Hat makes no representations about
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* the suitability of this software for any purpose.
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*
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* IN NO EVENT SHALL RED HAT BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT,
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* SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF
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* THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF RED HAT HAS BEEN ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* RED HAT DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND
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* RED HAT HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
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* ENHANCEMENTS, OR MODIFICATIONS.
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*/
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#ifndef __LINUX__AIO_ABI_H
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#define __LINUX__AIO_ABI_H
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#include <asm/byteorder.h>
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typedef unsigned long aio_context_t;
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enum {
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IOCB_CMD_PREAD = 0,
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IOCB_CMD_PWRITE = 1,
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IOCB_CMD_FSYNC = 2,
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IOCB_CMD_FDSYNC = 3,
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/* These two are experimental.
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* IOCB_CMD_PREADX = 4,
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* IOCB_CMD_POLL = 5,
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*/
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IOCB_CMD_NOOP = 6,
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IOCB_CMD_PREADV = 7,
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IOCB_CMD_PWRITEV = 8,
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};
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/*
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* Valid flags for the "aio_flags" member of the "struct iocb".
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*
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* IOCB_FLAG_RESFD - Set if the "aio_resfd" member of the "struct iocb"
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* is valid.
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*/
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#define IOCB_FLAG_RESFD (1 << 0)
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/* read() from /dev/aio returns these structures. */
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struct io_event {
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__u64 data; /* the data field from the iocb */
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__u64 obj; /* what iocb this event came from */
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__s64 res; /* result code for this event */
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__s64 res2; /* secondary result */
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};
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#if defined(__LITTLE_ENDIAN)
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#define PADDED(x,y) x, y
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#elif defined(__BIG_ENDIAN)
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#define PADDED(x,y) y, x
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#else
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#error edit for your odd byteorder.
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#endif
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/*
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* we always use a 64bit off_t when communicating
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* with userland. its up to libraries to do the
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* proper padding and aio_error abstraction
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*/
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struct iocb {
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/* these are internal to the kernel/libc. */
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__u64 aio_data; /* data to be returned in event's data */
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__u32 PADDED(aio_key, aio_reserved1);
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/* the kernel sets aio_key to the req # */
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/* common fields */
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__u16 aio_lio_opcode; /* see IOCB_CMD_ above */
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__s16 aio_reqprio;
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__u32 aio_fildes;
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__u64 aio_buf;
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__u64 aio_nbytes;
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__s64 aio_offset;
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/* extra parameters */
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__u64 aio_reserved2; /* TODO: use this for a (struct sigevent *) */
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/* flags for the "struct iocb" */
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__u32 aio_flags;
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/*
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* if the IOCB_FLAG_RESFD flag of "aio_flags" is set, this is an
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* eventfd to signal AIO readiness to
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*/
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__u32 aio_resfd;
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}; /* 64 bytes */
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#undef IFBIG
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#undef IFLITTLE
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#endif /* __LINUX__AIO_ABI_H */
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